Ciudad Hidalgo, Mexico
— This summer some 200 undocumented immigrants were hidden in a truck compartment when a floor holding more than a ton of bananas collapsed, killing six. The driver reportedly fled the scene.

For many it was a chilling reminder of another smuggling tragedy, when 19 undocumented immigrants suffocated in a trailer abandoned by its driver in Texas in 2003. Yet this time it was not a case of migrants trying to get into the US, but Central Americans trying to sneak into Mexico.

Mexico spends so much time fuming over its border relations with the US that its own southern frontier – where tens of thousands of Central Americans cross each year in hopes of making it to the US – is quite often an afterthought.

The country has traditionally been just a transit point on the immigration route, and has long been under pressure by the US to step up its security. Shortly after taking office in December, President Felipe Calderón responded to the call by setting up a new border police force with 645 officers.

But his administration is under equal pressure by critics who say Mexico demands of the US what it doesn't give to its own migrants: fair treatment.

Near the top of the list of demands for many immigrant rights activists is the decriminalization of the nation's immigration laws, which, in some cases, call for two years in prison for being undocumented.

"Migration has changed," says Fermina Rodriguez, a human rights coordinator in the southern town of Tapachula. "[Mexican authorities] should view Mexico as a destination, not just a country of transit or expulsion of immigrants."

Mexico's southern frontier is hardly an obstacle at all – at least when comparing it with the censors, radar, and border patrol agents that man the US-Mexico border. Here in the border town of Ciudad Hidalgo, drugs, weapons, and people pass illegally over the Suchiate River at any time of the day.

Jorge Mario Garcia, from Guatemala, recently crossed the river in broad daylight. His friends each paid $1 to ride on inner tubes run as a mini ferry service. He opted to swim the stretch himself. "It's a thousand times easier to cross into Mexico than the US," says Mr. Garcia, who was caught and deported from McCallen, Texas just a few months earlier.

The number of Central Americans caught attempting to get into Mexico rose to 240,200 in 2005 from 138,000 in 2002, according to the National Migration Institute. That number dipped to 182,700 last year, but is expected to rise sharply to 205,000 this year.

But crossing the border is often the easiest part. Surviving along the frontier, paying off bribes, avoiding gangs, and dodging thieves who pray on migrants with cash in their pockets, make up the stories of migrants in shelters in this region of Chiapas.

Mr. Garcia, who was recuperating at a shelter from a 24-hour walk from the Mexico border along washed out railway tracks to Tapachula – during which he and his friends were robbed and beaten – says his intent is to make it to Los Angeles, to meet his mother.

But he says he won't be surprised if he stays in Mexico for a while this time. When his friends and neighbors fail to reach the US, he says, they just set out again.

But it gets tiring, he says, dunking two chickens by their feet into a simmering pot of water. "The goal of all of us is to get to the US," he says. "But to be honest … the US isn't going anywhere. If we can find an opportunity in Mexico to work for a while and save some money, we will."

While President Calderón's first step was to create a new police task force in Chiapas, where most migrants are caught, most of the administration's initiatives have centered on better treatment for migrants. Mexico's legislature is debating changes to the immigration law, including changing the penalty for entering the country illegally to a civil violation instead of a crime punishable with jail time.

The National Migration Institute announced improvements to the nation's 48 detention centers and human rights training for its officials. According to a spokeswoman from the institute, they will also be releasing details of a Safe Southern Border Program to clamp down on gangs, corruption, and trafficking along the southern border.

"For the migrants that try to cross [Mexico's] national territory, we can't give less guarantees than those we demand for Mexican migrants," Cecilia Romero, the head of the migration institute, said in December.

On a recent day, Francisco Aceves, the coordinator for Grupos Beta, a government agency that helps migrants, loads up his orange pickup truck with cans of tuna and water for 100 and drives off toward the border. He scours washed out train tracks that still guide the migrants' journeys.

He says that corruption is what makes his job hardest. His group hands out pamplets to migrants, educating them on how to avoid being extorted for money. "But we are working against a very big monster," he says.

Raúl Benítez, a security expert at the Center for North American Studies at the National Autonomous University of Mexico, agrees. He says that corruption plagues efforts to both ease immigration and improve human rights. Often, he says, migrants pay small bribes to five or six different officials as they cross into Mexico, showing the multiple layers of the problem. "It is extortion of the migrants," Mr. Benítez says.

The number of illegal immigrants deported by US Immigration and Customs Enforcement has nearly doubled since 2001.

Veronica Nur Valdes, a spokeswoman for the US Department of Homeland Security, says the US supports Calderón's resolve to seal its southern border.

Some resent what they consider as Mexico playing vigilante to the US. Carmen Fernandez, an expert of immigration studies at the College of the Southern Border in Tapachula, says that the fact that the border is so easy to pass, and yet immigrants are caught along the way reveals a motive. "It's a palpable sign that migration [policy] is for the US, not for Mexico," Ms. Fernandez says.

But Ms. Rodriguez says that increased security alone will do nothing to stop the flow – the same argument that Mexicans make against the possible US construction of a 700-mile border fence. "The more police agencies we have, the more human rights are violated," she says. "If they close the path, they'll find a more dangerous path."

That is the case with Luis Antonio Montenegro, from Nicaragua, who is making his first attempt to get into the US. He wants to go to Houston, because it's the closest big city, to work in construction, or anything he can find. Anything else. "I've worked uninterrupted since age 14 and haven't been able to do anything with it, buy own my own house or own my business," he says. "I'm afraid, but I have to persevere."